Hindawi Publishing Corporation Journal of Parasitology Research Volume 2012, Article ID 748540, 7 pages doi:10.1155/2012/748540
Research Article Transmission of Onchocerciasis in Wadelai Focus of Northwestern Uganda Has Been Interrupted and the Disease Eliminated Moses N. Katabarwa,1 Frank Walsh,2 Peace Habomugisha,3 Thomson L. Lakwo,4 Stella Agunyo,3 David W. Oguttu,4 Thomas R. Unnasch,5 Dickson Unoba,6 Edson Byamukama,3 Ephraim Tukesiga,7 Richard Ndyomugyenyi,4 and Frank O. Richards1 1 Emory
University and The Carter Center, One Copenhill, 453 Freedom Parkway, Atlanta, GA 30307, USA Arundel Road, Lythan St. Anne’s, Lancashire FY8 1BN, UK 3 The Carter Center, Uganda, P.O. Box 12027, Kampala, Uganda 4 Vector Control Division, Ministry of Health, 15 Bombo Road, P.O. Box 1661, Kampala, Uganda 5 Global Health Infectious Disease Research, College of Public Health, University of South Florida 3720 Spectrum Boulevard, Suite 304, Tampa, FL 33612, USA 6 Nebbi District Health Services, P.O. Box 1, Nebbi, Uganda 7 Kabarole District Health Services, P.O. Box 38, Kabarole, Uganda 2 80
Correspondence should be addressed to Moses N. Katabarwa,
[email protected] Received 26 March 2012; Revised 29 June 2012; Accepted 6 July 2012 Academic Editor: Vitaliano A. Cama Copyright © 2012 Moses N. Katabarwa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Wadelai, an isolated focus for onchocerciasis in northwest Uganda, was selected for piloting an onchocerciasis elimination strategy that was ultimately the precursor for countrywide onchocerciasis elimination policy. The Wadelai focus strategy was to increase ivermectin treatments from annual to semiannual frequency and expand geographic area in order to include communities with nodule rate of less than 20%. These communities had not been covered by the previous policy that sought to control onchocerciasis only as a public health problem. From 2006 to 2010, Wadelai program successfully attained ultimate treatment goal (UTG), treatment coverage of ≥90%, despite expanding from 19 to 34 communities and from 5,600 annual treatments to over 29,000 semiannual treatments. Evaluations in 2009 showed no microfilaria in skin snips of over 500 persons examined, and only 1 of 3011 children was IgG4 antibody positive to the OV16 recombinant antigen. No Simulium vectors were found, and their disappearance could have sped up interruption of transmission. Although twice-per-year treatment had an unclear role in interruption of transmission, the experience demonstrated that twice-per-year treatment is feasible in the Ugandan setting. The monitoring data support the conclusion that onchocerciasis has been eliminated from the Wadelai focus of Uganda.
1. Introduction The Wadelai onchocerciasis focus is one of the smallest in Uganda, comprising only about 15,000 people living close to the lower River Ora in the Nebbi district. It is not clear when this focus first came to the attention of the health authorities, but in 1951 onchocerciasis was recognised in the upper reaches of the River Aroga (a major tributary of the River Ora). The vector was assumed to be Simulium neavei [1] based on the forested environment. Much more was
learnt of the distribution of onchocerciasis and its vectors in the following two decades. The breeding of a non-man-biting form of S. damnosum s.l, was reported in 1966 along River Ali, located opposite Rhino Camp roughly 15 kilometres downstream of the River Ora outfall [2, 3]. Barnley in his lecture notes delivered at Makerere University in 1968 entitled “The Distribution of Onchocerciasis and its Vectors in Uganda”, confirmed that S. neavei was the vector in the upper reaches of River Ora system, but made no mention of the situation in its lower reaches where the Wadelai focus is
2 located [4]. Later in the Uganda Atlas of disease distribution, Barnley gave a distribution map of onchocerciasis and its vectors showing the presence of a small onchocerciasis focus in Wadelai, and in the vicinity of the River Ora outfall in the Albert Nile transmitted by S. damnosum s.l [5]. As such, it became a target for piloting the elimination approach in late 2005.
2. Methods 2.1. Baseline Parasitological (Nodule and Skin Snips) Assessment in 1993 2.1.1. Nodule Assessment. Rapid epidemiological mapping of onchocerciasis (REMO) and rapid epidemiological assessment (REA) was conducted by nodule palpation with the assistance of River Blindness Foundation (RBF) and WHO/TDR throughout Nebbi district of north-western Uganda including the Wadelai area [6–8]. Based on REMO protocol for community selection, only one community (Olimbuni/Aroga) was selected for mapping and as a sentinel site in 1993. REMO is where “high risk” communities are first identified at every 30 km along the river, and additional primary communities located 10 km away from “high risk” ones are selected. If warranted, then secondary communities 10 km away from primary communities and tertiary communities 10 km from secondary communities are selected until onchocercal nodule-free communities are reached. Assessment of nodule rates was done among 30 adults of at least 20 years of age who had lived in the community for 20 years or more [7]. The results were expressed as a proportion of the number of positive/negative persons in the sample. 2.1.2. Skin Snips Microfilariae (mf) Assessment. Skin snips were also obtained from 50 adults in the same community (Olimbuni/Aroga) before mass treatment. The tip of a sterile lancet needle mounted in a holder was used to elevate 34 mm of skin over the right posterior superior iliac crest after cleansing the skin with alcohol. A sterile surgical razor blade was then used to remove a skin snip at the base of the elevation. The skin, dangling from the tip of the needle, was transferred to a well of 96 microtiter plate containing sterile normal saline solution. The blade and needle were then used to obtain the second specimen on the left side in the same manner, after which the needle and blade were discarded in an appropriately safe “sharps” container [6, 9]. The use of a disposable razor and needle is a government policy in order to avoid transmission of communicable diseases such as HIV/AIDS and hepatitis, as well as providing the program with standard tools that are affordable and readily available in the country. The skin snips were kept at room temperature in the microtiter plate in normal saline solution for 12–24 h to allow any mf present to emerge from the skin. Each skin snip was then removed from the well with a needle, and the saline solution was examined unstained under a microscope (40x) for mf of O. volvulus. The results were expressed as a proportion of the number of positive/negative persons in the sample.
Journal of Parasitology Research Parasitological (nodule palpation and skin snips) assessments were carried out during 1993 in Olimbuni/Aroga community, prior to annual mass treatment with ivermectin. Wadelai focus was demonstrated to be isolated from other onchocerciasis endemic communities in the area (see Figure 1 title below). 2.2. Mass Treatment. Annual mass treatment with ivermectin commenced in 1993 when 2,593 persons were treated. In 1993 community-based treatment was introduced with the support of the River Blindness Foundation and in 1999 communities were empowered to make their own decisions under community-directed treatment with ivermectin (CDTI) [10]. Under CDTI, treatments grew to 5682 in 19 communities by 2005. When elimination effort was piloted in 2006, semiannual (i.e. every six month) distribution was launched, and, in 2007, geographic coverage was expanded to include all 34 communities in Wadelai area encompassing communities with nodule rate less than 20% representing, “full geographic coverage” (Figure 2) [11]. Such communities were previously not considered for mass treatment with ivermectin under the policy for controlling onchocerciasis as a public health problem [12]. Therefore, launching of elimination policy resulted in a considerable expansion of treatments to over 29,000 by 2010. In spite of the change from a single annual dose to semi-annual dose of ivermectin, ultimate treatment goal (UTG) was attained every year. UTG is the sum of all eligible persons for treatment (minus children
